Is it possible to use the input property [columns], together with the ngx-datatable-column directive?

Question

So I am working on a feature for the table in my app. I have done an abstraction over the ngx-datatable as a component which acts as a facade for other components in my app (someComponent => FacadeTableComponent => Ngx-DataTable).

The columns are created in the FacadeTableComponent based on someComponent, and passed as an input to the NgxDataTable.

But now I want to add a tree view to the datatable (that works) but I want the FacadeTableComponent to set a default first column with a button that does the tree collapsing/expanding. So I thought that the default column could be defined as a ngx-datatable-column in the FacadeTableComponent html template. The problem seems that the input columns seem to overwrite my default column.

Now I tried to somehow grab the ngx-datatable-column with a @ViewChild and unshift it to the generated columns in the FacadeTableComponent, but I am not able to grab it as a directive, rather as a ElementRef.

I could of course just define a default column in the .ts file and generate it when I generate the rest of the columns, but I want to know if it is possible to do it the way I described it in the title.

The reason for this default column is that when I set one of the existing columns as a treeView column, the ngx datatable adds a default button, even if I provide my own template to the cell, and I want to provide my own button in the template.

<ngx-datatable #ngxDataTable class="datatable" [rows]="collection" [columnMode]="columnMode"
        [footerHeight]="footerHeight" [selectionType]="selectionType" [sortType]="sortType" [sorts]="sorts"
        [rowIdentity]="rowIdentity" [messages]="tableMessages" [selected]="selectedRows" [columns]="columns"
        [headerHeight]="headerHeight" [rowHeight]="rowHeight" [scrollbarV]="true" [scrollbarH]="true"
        (select)="onSelect($event)" (activate)="onActive($event)" [externalSorting]="true" [rowClass]="rowCssClass"
        [sortType]="'single'" [treeFromRelation]="'MasterId'" [treeToRelation]="'id'"
        (treeAction)="onTreeAction($event)" (sort)="sortRows($event)" (resize)="resizeTriggered($event)"> 

        <!-- Datatable tree view column -->
        <ngx-datatable-column #column_tree_view name="Tree" [isTreeColumn]="true" [width]="150"
            [treeLevelIndent]="20">
            <ng-template ngx-datatable-tree-toggle let-tree="cellContext">
                <button [disabled]="tree.treeStatus==='disabled'" (click)="tree.onTreeAction()">
                    <span *ngIf="tree.treeStatus==='loading'">
                        ...
                    </span>
                    <span *ngIf="tree.treeStatus==='collapsed'">
                        ↑
                    </span>
                    <span *ngIf="tree.treeStatus==='expanded'">
                        ↓
                    </span>
                    <span *ngIf="tree.treeStatus==='disabled'">
                        ⃠
                    </span>
                </button>
            </ng-template>
        </ngx-datatable-column>
<ngx-datatable>

Answer 1

I already solved it if someone stomps upon this question:

Firs we define an ng-template on the html of the FacadeTableComponent:

<ng-template #treeTemplate let-row="row">
<div *ngIf="row.IsTreeColumn" class="tree-cell">
    <ng-container *ngTemplateOutlet="treeColumnTemplate; context: {row : row}"></ng-container>
    <p-button (click)="onTreeAction(row)">
        <span *ngIf="row.treeStatus==='collapsed'">
            ↑
        </span>
        <span *ngIf="row.treeStatus==='expanded'">
            ↓
        </span>
    </p-button>
</div>

After that I just grab the template with the directive viewChild, define a column with the prop value of '_treeColumnName', which is provided as an input of the Facade and unshift it to the columns array:

@ViewChild('treeTemplate') private _treeViewTemplate: TemplateRef<any>;


private createTreeViewColumn(): void {
    const column: TableColumn= {
        name: this._treeColumnName,
        prop: this._treeColumnName,
    } as TableColumn;

    if (this.columns.findIndex((tablecolumn: TableColumn) => tablecolumn.prop === this._treeColumnName) === -1) {
        // the isTreeColumn is not included in the TableColumn, therefore a cast is needed
        const tablecolumn = column as TableColumn;
        tablecolumn.isTreeColumn = true;
        this.columns.unshift(tablecolumn);
    }
}

private removeTreeViewColumn(): void {
    const treecolumnindex = this.columns.findIndex((tablecolumn: TableColumn) => tablecolumn.prop === this._treeColumnName);
    if (treecolumnindex !== -1) {
        this.columns.splice(treecolumnindex, 1);
    }
}

Finally I just add the implementation to the expand/collapse feature:

    private readonly _treeStatusCollapsed: string = 'collapsed';
    private readonly _treeStatusExpanded: string = 'expanded';

    ... 

    /** Expands or collapses a tree view row
     */
    public onTreeAction(event: any): void {
        const row = event;
        if (row.treeStatus === this._treeStatusCollapsed) {
            row.treeStatus = this._treeStatusExpanded;
        } else {
            row.treeStatus = this._treeStatusCollapsed;
        }
            // trigger a change detection
            this.rows= [...this.rows];
            this._changeDetectorRef.detectChanges();
        }

And that is it, works like a charm. Of course one could then provida whatever template it wants, or via css classes change the icons.